1. Field of the Invention
The present invention relates to a diversity apparatus using a leakage transmission path as an antenna.
2. Description of the Related Art
A conventional antenna device using a leaky coaxial cable with which a diversity system is employed is known. In Jpn. Pat. Appln. KOKAI Publication No. 8-298473, two systems are disclosed as antenna devices of this type.
In an antenna device of the first system, one leaky coaxial cable is used. A transceiver and a terminal resistor are selectively connected to one end of the leaky coaxial cable by a switch. The transceiver and another terminal resistor are selectively connected to the other end of the leaky coaxial cable by another switch.
When the transceiver is connected to one end of the leaky coaxial cable, the terminal resistor is connected to the other end of the leaky coaxial cable. In this state, when an antenna device of a mobile object is located in a radio wave dead zone, each switch is changed over. As a result, the terminal resistor is connected to one end of the leaky coaxial cable, and the transceiver is connected to the other end thereof. In this manner, a diversity effect is obtained.
In an antenna device of the second system, two leaky coaxial cables are used. The two leaky coaxial cables are arranged parallel to each other. A transceiver is connected to one end of one leaky coaxial cable through a switch. A terminal resistor is connected to the other end of one leaky coaxial cable. The same transceiver is connected to one end of another leaky coaxial cable through the same switch. Another terminal resistor is connected to the other end of the other leaky coaxial cable. One end of the other leaky coaxial cable and the other end of one leaky coaxial cable are on the same side.
In use of one leaky coaxial cable, when an antenna device of a mobile object is located in a radio wave dead zone, the switch is changed over. As a result, the other leaky coaxial cable is in use. In this manner, a diversity effect is obtained.
However, each of the first and second antenna devices is entirely arranged in the form of a loop. For this reason, the lay-down of the leaky coaxial cable is disadvantageously limited.